[mythtv] New MPEG2 commercial-cut code ready for testing

[Bryan Mayland]

Geoffrey Hausheer wrote:
> Have you tried replacing the malloc with a memalign(16,
> outbuf_size)?  
    Yeah I had tried that yesterday and it was still giving me the segv, 
so I started digging into libavcodec since it seemed to be the problem.  
About 30 minutes into it, I went digging in the svn log for the 
mpegvideo_mmx_template.c thinking I was seeing a regression, then saw 
the changes in HEAD.  So it turned out to be not mpeg2fix related at all.

mpeg2fix-0.10 works great, no infinite loops, no segfaults.  Just 
QMAT_SHIFTs.  I'll check the quality on the resultant cuts later today 
for blockiness or other artifacts.  Thanks for all your work so far!